Re: [PATCH 8/8] drm/i915: Do remaps for all contexts

Ville Syrjälä
2013-09-13T09:17:21Z

On Thu, Sep 12, 2013 at 10:28:34PM -0700, Ben Widawsky wrote:
> On both Ivybridge and Haswell, row remapping information is saved and
> restored with context. This means, we never actually properly supported
> the l3 remapping because our sysfs interface is asynchronous (and not
> tied to any context), and the known faulty HW would be reused by the
> next context to run.
>
> Not that due to the asynchronous nature of the sysfs entry, there is no
> point modifying the registers for the existing context. Instead we set a
> flag for all contexts to load the correct remapping information on the
> next run. Interested clients can use debugfs to determine whether or not
> the row has been remapped.
>
> One could propose at this point that we just do the remapping in the
> kernel. I guess since we have to maintain the sysfs interface anyway,
> I'm not sure how useful it is, and I do like keeping the policy in
> userspace; (it wasn't my original decision to make the
> interface the way it is, so I'm not attached).
>
> Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
> ---
> drivers/gpu/drm/i915/i915_debugfs.c | 8 +++++++
> drivers/gpu/drm/i915/i915_drv.h | 1 +
> drivers/gpu/drm/i915/i915_gem_context.c | 17 +++++++++++++--
> drivers/gpu/drm/i915/i915_sysfs.c | 38 +++++++++++----------------------
> 4 files changed, 36 insertions(+), 28 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
> index ada0950..80bed69 100644
> --- a/drivers/gpu/drm/i915/i915_debugfs.c
> +++ b/drivers/gpu/drm/i915/i915_debugfs.c
> @@ -145,6 +145,13 @@ describe_obj(struct seq_file *m, struct drm_i915_gem_object *obj)
> seq_printf(m, " (%s)", obj->ring->name);
> }
>
> +static void describe_ctx(struct seq_file *m, struct i915_hw_context *ctx)
> +{
> + seq_putc(m, ctx->is_initialized ? 'I' : 'i');
> + seq_putc(m, ctx->remap_slice ? 'R' : 'r');
> + seq_putc(m, ' ');
> +}
> +
> static int i915_gem_object_list_info(struct seq_file *m, void *data)
> {
> struct drm_info_node *node = (struct drm_info_node *) m->private;
> @@ -1463,6 +1470,7 @@ static int i915_context_status(struct seq_file *m, void *unused)
>
> list_for_each_entry(ctx, &dev_priv->context_list, link) {
> seq_puts(m, "HW context ");
> + describe_ctx(m, ctx);
> for_each_ring(ring, dev_priv, i)
> if (ring->default_context == ctx)
> seq_printf(m, "(default context %s) ", ring->name);
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 68f992b..6ba78cd 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -602,6 +602,7 @@ struct i915_hw_context {
> struct kref ref;
> int id;
> bool is_initialized;
> + uint8_t remap_slice;
> struct drm_i915_file_private *file_priv;
> struct intel_ring_buffer *ring;
> struct drm_i915_gem_object *obj;
> diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
> index 2bbdce8..72b7202 100644
> --- a/drivers/gpu/drm/i915/i915_gem_context.c
> +++ b/drivers/gpu/drm/i915/i915_gem_context.c
> @@ -140,7 +140,7 @@ create_hw_context(struct drm_device *dev,
> {
> struct drm_i915_private *dev_priv = dev->dev_private;
> struct i915_hw_context *ctx;
> - int ret;
> + int ret, i;
>
> ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
> if (ctx == NULL)
> @@ -181,6 +181,8 @@ create_hw_context(struct drm_device *dev,
>
> ctx->file_priv = file_priv;
> ctx->id = ret;
> + for (i = 0; i < NUM_L3_SLICES(dev); i++)
> + ctx->remap_slice |= 1 << 1;
^
i

>
> return ctx;
>
> @@ -396,7 +398,7 @@ static int do_switch(struct i915_hw_context *to)
> struct intel_ring_buffer *ring = to->ring;
> struct i915_hw_context *from = ring->last_context;
> u32 hw_flags = 0;
> - int ret;
> + int ret, i;
>
> BUG_ON(from != NULL && from->obj != NULL && from->obj->pin_count == 0);
>
> @@ -432,6 +434,17 @@ static int do_switch(struct i915_hw_context *to)
> return ret;
> }
>
> + for (i = 0; i < MAX_L3_SLICES; i++) {
> + if (!(to->remap_slice & (1<<i)))
> + continue;
> +
> + ret = i915_gem_l3_remap(ring, i);
> + if (!ret) {
> + to->remap_slice &= ~(1<<i);
> + }
> + /* If it failed, try again next round */
> + }
> +
> /* The backing object for the context is done after switching to the
> * *next* context. Therefore we cannot retire the previous context until
> * the next context has already started running. In fact, the below code
> diff --git a/drivers/gpu/drm/i915/i915_sysfs.c b/drivers/gpu/drm/i915/i915_sysfs.c
> index 65a7274..f0d7e1c 100644
> --- a/drivers/gpu/drm/i915/i915_sysfs.c
> +++ b/drivers/gpu/drm/i915/i915_sysfs.c
> @@ -118,9 +118,8 @@ i915_l3_read(struct file *filp, struct kobject *kobj,
> struct drm_minor *dminor = container_of(dev, struct drm_minor, kdev);
> struct drm_device *drm_dev = dminor->dev;
> struct drm_i915_private *dev_priv = drm_dev->dev_private;
> - uint32_t misccpctl;
> int slice = (int)(uintptr_t)attr->private;
> - int i, ret;
> + int ret;
>
> count = round_down(count, 4);
>
> @@ -134,31 +133,16 @@ i915_l3_read(struct file *filp, struct kobject *kobj,
> if (ret)
> return ret;
>
> - if (IS_HASWELL(drm_dev)) {
> - int last = min_t(int, GEN7_L3LOG_SIZE, count + offset);
> - if ((!dev_priv->l3_parity.remap_info[slice]))
> - memset(buf + offset, 0, last - offset);
> - else
> - memcpy(buf + offset,
> - dev_priv->l3_parity.remap_info[slice] + (offset/4),
> - last - offset);
> -
> - i = last;
> - goto out;
> - }
> -
> - misccpctl = I915_READ(GEN7_MISCCPCTL);
> - I915_WRITE(GEN7_MISCCPCTL, misccpctl & ~GEN7_DOP_CLOCK_GATE_ENABLE);
> -
> - for (i = 0; i < count; i += 4)
> - *((uint32_t *)(&buf[i])) = I915_READ(GEN7_L3LOG_BASE + offset + i);
> -
> - I915_WRITE(GEN7_MISCCPCTL, misccpctl);
> + if ((!dev_priv->l3_parity.remap_info[slice]))
> + memset(buf + offset, 0, count);
> + else
> + memcpy(buf + offset,
> + dev_priv->l3_parity.remap_info[slice] + (offset/4),
> + count);

Needs fixing after patch 4 is fixed.

>
> -out:
> mutex_unlock(&drm_dev->struct_mutex);
>
> - return i;
> + return count;
> }
>
> static ssize_t
> @@ -170,6 +154,7 @@ i915_l3_write(struct file *filp, struct kobject *kobj,
> struct drm_minor *dminor = container_of(dev, struct drm_minor, kdev);
> struct drm_device *drm_dev = dminor->dev;
> struct drm_i915_private *dev_priv = drm_dev->dev_private;
> + struct i915_hw_context *ctx;
> u32 *temp = NULL; /* Just here to make handling failures easy */
> int slice = (int)(uintptr_t)attr->private;
> int ret;
> @@ -206,8 +191,9 @@ i915_l3_write(struct file *filp, struct kobject *kobj,
>
> memcpy(dev_priv->l3_parity.remap_info[slice] + (offset/4), buf, count);
>
> - if (i915_gem_l3_remap(&dev_priv->ring[RCS], slice))
> - count = 0;
> + /* NB: We defer the remapping until we switch to the context */
> + list_for_each_entry(ctx, &dev_priv->context_list, link)
> + ctx->remap_slice |= (1<<slice);

Should we force a context switch on the next batch if the current
context has remap_slice != 0?

Also what happens if hw_contexts_disabled==false?

>
> mutex_unlock(&drm_dev->struct_mutex);
>
> --
> 1.8.4
>
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--
Ville Syrjälä
Intel OTC